Fig. 12

IGRF12 retroactive SV comparison at Honolulu (HON). Left panels show the observatory annual differences of daily mean values (black), annual spline difference curve (red) and IGRF12 candidate predictions for the \({\text{d}}B_x/{\text{d}}t\) (top), \({\text{d}}B_y/{\text{d}}t\) (middle), and \({\text{d}}B_z/{\text{d}}t\) (bottom) components in the NEC frame. Right panels show the original observatory data (blue), data after selecting for geomagnetically quiet periods (green), and fitted spline curve (black) for the \(B_x\) (top), \(B_y\) (middle) and \(B_z\) (bottom) components